Metrology and analysis

Check the basics of semiconductor metrology and analysis — SEM and TEM, ellipsometry, SIMS and four-point probe — with multiple-choice questions.

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Metrology and analysis: key points

In semiconductor manufacturing, line widths, film thicknesses, impurity concentrations and defects are measured along the way to confirm that each process is working correctly. The finer the features, the more accurate nanometer-scale measurement must be.

Different methods are used for different purposes: electron microscopes (SEM and TEM) for shape, ellipsometry for film thickness, secondary ion mass spectrometry (SIMS) for impurity profiles, and the four-point probe for sheet resistance.

All Metrology and analysis questions (50)

  1. Which correctly describes the principle of the scanning electron microscope (SEM)?
  2. What is mainly measured by ellipsometry (spectroscopic ellipsometry)?
  3. Which correctly describes SIMS (secondary ion mass spectrometry)?
  4. What is mainly measured by the four-point probe method?
  5. Which correctly describes the sample preparation needed to observe a sample with a transmission electron microscope (TEM)?
  6. Which is a typical principle used in defect inspection tools that detect particles and pattern defects on wafers?
  7. What is mainly measured with an atomic force microscope (AFM)?
  8. What can be determined with EDX (energy-dispersive X-ray spectroscopy), used together with SEM and TEM?
  9. Which method is often used to analyze trace metal contamination on wafer surfaces?
  10. Which can be evaluated from C-V (capacitance-voltage) measurements of a MOS capacitor?
  11. What is the measurement called that shines light on periodic patterns and compares the spectrum of reflected and diffracted light with a model to determine linewidth and cross-sectional shape?
  12. What can mainly be evaluated by X-ray diffraction (XRD)?
  13. What are the main uses of focused ion beam (FIB) systems?
  14. Which analysis method determines surface elements and their chemical bonding states from the energies of photoelectrons emitted under X-ray irradiation?
  15. Which analysis technique locates failures in an LSI by detecting faint light emitted from defective sites during operation?
  16. When ArF resist patterns are measured with a CD-SEM, what is the phenomenon called in which electron-beam irradiation makes the patterns shrink?
  17. What is placed on the wafer to measure overlay error?
  18. Which technique directs X-rays at a very shallow angle and determines thin-film thickness and density from oscillations in reflectivity?
  19. Which method is used to measure wafer bow, warp and flatness?
  20. Which technique evaluates whether a measuring instrument's repeatability and reproducibility are small enough compared with the process variation to be controlled?
  21. What is the main reason fine patterns a few tens of nm wide cannot be observed directly with an optical microscope?
  22. Which equation is used to determine film stress from the change in wafer bow before and after deposition?
  23. Whereas SIMS measures the atomic concentration of impurities, which method measures the depth distribution of electrically active carrier concentration?
  24. What is the measurement called that monitors a process by measuring product wafers partway through processing on the production line?
  25. Which inspection detects defects such as contact open failures using differences in brightness caused by differences in charging under an electron beam?
  26. When observing insulating samples with an SEM, which is a correct way to prevent charging (charge-up)?
  27. Which technology is being researched and introduced to measure shapes such as deep holes three-dimensionally without cutting cross-sections?
  28. Which method is used to measure interstitial oxygen concentration in silicon?
  29. Which method measures wafer carrier lifetime without contact to evaluate metal contamination and the like?
  30. Which function captures SEM images of defects found in inspection and automatically classifies their types from the images?
  31. Which correctly describes the general difference between "metrology" and "inspection" on a semiconductor production line?
  32. What is the main purpose of performing metrology and inspection partway through the process on a production line?
  33. In production-line metrology, why are only selected wafers or points often measured rather than all of them?
  34. Which correctly describes observing a cross-section in detail after breaking or milling the wafer?
  35. Which pair correctly names a measuring instrument's property of "small spread when measuring the same thing repeatedly" and that of "measured values being close to the true value"?
  36. Which spectroscopic method is often used to evaluate stress (strain) in silicon locally and non-destructively?
  37. Which method is used to observe solder joint voids and wire shapes inside a package in three dimensions without destroying it?
  38. Which tool is widely used to find delamination at interfaces inside a package, such as between molding compound and chip, non-destructively?
  39. Which method evaluates the quality of compound semiconductor wafers and epi layers without contact by shining laser light and measuring the spectrum and intensity distribution of the emitted light?
  40. Compared with bright-field wafer inspection, which images patterns directly, what characterizes dark-field inspection, which captures only scattered light?
  41. Which instrument traces a sample surface with a fine stylus and measures step heights and surface shape from the stylus's vertical motion?
  42. What is the technique called that uses statistical models to predict film thickness or dimensions of wafers that were not actually measured, from equipment sensor data and the like?
  43. When measuring very narrow trenches or steep sidewalls with AFM, what tends to cause errors?
  44. In TEM, which technique scans a finely focused electron beam and measures the energy lost by transmitted electrons to map elements and chemical states?
  45. Which analysis method field-evaporates atoms one by one from the tip of a needle-shaped specimen and detects their positions and identities to map the 3D distribution of atoms such as dopants?
  46. Which method, without forming electrodes, deposits charge on the wafer surface by corona discharge and measures changes in surface potential to evaluate oxide and interface electrical properties?
  47. Which technique locates faults by detecting tiny heat generation in a powered chip with high sensitivity, periodically modulating the applied power and accumulating synchronized thermal images?
  48. Which method sends fast pulses into package or board wiring and determines the location of opens or shorts from the reflected waveforms?
  49. In optical defect inspection, why does detection become sharply harder as particles get smaller?
  50. What is the approach called that combines data from multiple measurement methods (optical, CD-SEM, AFM and so on) to determine dimensions and shapes more accurately than any single method?

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